<style>
    .map-overlay {
        font: 12px/20px 'Helvetica Neue', Arial, Helvetica, sans-serif;
        position: absolute;
        width: 200px;
        top: 0;
        left: 0;
        padding: 10px;
    }

    .map-overlay .map-overlay-inner {
        background-color: #fff;
        box-shadow: 0 1px 2px rgba(0, 0, 0, 0.1);
        border-radius: 3px;
        padding: 10px;
        margin-bottom: 10px;
    }

    .map-overlay-inner fieldset {
        border: none;
        padding: 0;
        margin: 0 0 10px;
    }

    .map-overlay-inner fieldset:last-child {
        margin: 0;
    }

    .map-overlay-inner select {
        width: 100%;
    }

    .map-overlay-inner p {
        margin: 0;
    }

    .map-overlay-inner label {
        display: block;
        font-weight: bold;
    }

    .map-overlay-inner button {
        background-color: cornflowerblue;
        color: white;
        border-radius: 5px;
        display: inline-block;
        height: 20px;
        border: none;
        cursor: pointer;
    }

    .map-overlay-inner button:focus {
        outline: none;
    }

    .map-overlay-inner button:hover {
        background-color: blue;
        box-shadow: inset 0 0 0 3px rgba(0, 0, 0, 0.1);
        -webkit-transition: background-color 500ms linear;
        -ms-transition: background-color 500ms linear;
        transition: background-color 500ms linear;
    }

    .offset > label,
    .offset > input {
        display: inline;
    }

    #animateLabel {
        display: inline-block;
        min-width: 20px;
    }
</style>

<div id="map"></div>
<div class="map-overlay top">
    <div class="map-overlay-inner">
        <fieldset>
            <label>Select easing function</label>
            <select id="easing" name="easing">
                <option value="easeInCubic">Ease In Cubic</option>
                <option value="easeOutQuint">Ease Out Quint</option>
                <option value="easeInOutCirc">Ease In/Out Circ</option>
                <option value="easeOutBounce">Ease Out Bounce</option>
            </select>
        </fieldset>
        <fieldset>
            <label for="duration">Set animation duration</label>
            <p id="durationValue"></p>
            <input
                type="range"
                id="duration"
                name="duration"
                min="0"
                max="10000"
                step="500"
                value="1000"
            />
        </fieldset>
        <fieldset>
            <label>Animate camera motion</label>
            <label for="animate" id="animateLabel">Yes</label>
            <input type="checkbox" id="animate" name="animate" checked />
        </fieldset>
        <fieldset class="offset">
            <label for="offset-x">Offset-X</label>
            <input
                type="number"
                id="offset-x"
                name="offset-x"
                min="-200"
                max="200"
                step="50"
                value="0"
            />
        </fieldset>
        <fieldset class="offset">
            <label for="offset-y">Offset-Y</label>
            <input
                type="number"
                id="offset-y"
                name="offset-y"
                min="-200"
                max="200"
                step="50"
                value="0"
            />
            <p>Offsets can be negative</p>
        </fieldset>
        <button type="button" id="animateButton" name="test-animation">
            Test Animation
        </button>
    </div>
</div>

<script>
    // declare various easing functions.
    // easing functions mathematically describe
    // how fast a value changes during an animation.
    // each function takes a parameter t that represents
    // the progress of the animation.
    // t is in a range of 0 to 1 where 0 is the initial
    // state and 1 is the completed state.
    var easingFunctions = {
        // start slow and gradually increase speed
        easeInCubic: function(t) {
            return t * t * t;
        },
        // start fast with a long, slow wind-down
        easeOutQuint: function(t) {
            return 1 - Math.pow(1 - t, 5);
        },
        // slow start and finish with fast middle
        easeInOutCirc: function(t) {
            return t < 0.5
                ? (1 - Math.sqrt(1 - Math.pow(2 * t, 2))) / 2
                : (Math.sqrt(1 - Math.pow(-2 * t + 2, 2)) + 1) / 2;
        },
        // fast start with a "bounce" at the end
        easeOutBounce: function(t) {
            var n1 = 7.5625;
            var d1 = 2.75;

            if (t < 1 / d1) {
                return n1 * t * t;
            } else if (t < 2 / d1) {
                return n1 * (t -= 1.5 / d1) * t + 0.75;
            } else if (t < 2.5 / d1) {
                return n1 * (t -= 2.25 / d1) * t + 0.9375;
            } else {
                return n1 * (t -= 2.625 / d1) * t + 0.984375;
            }
        }
    };

    // set up some helpful UX on the form
    var durationValueSpan = document.getElementById('durationValue');
    var durationInput = document.getElementById('duration');
    durationValueSpan.innerHTML = durationInput.value / 1000 + ' seconds';
    durationInput.addEventListener('change', function(e) {
        durationValueSpan.innerHTML = e.target.value / 1000 + ' seconds';
    });

    var animateLabel = document.getElementById('animateLabel');
    var animateValue = document.getElementById('animate');
    animateValue.addEventListener('change', function(e) {
        animateLabel.innerHTML = e.target.checked ? 'Yes' : 'No';
    });

    var map = new mapboxgl.Map({
        container: 'map',
        style: 'mapbox://styles/mapbox/streets-v11',
        center: [-95, 40],
        zoom: 3
    });

    map.on('load', function() {
        // add a layer to display the map's center point
        map.addSource('center', {
            'type': 'geojson',
            'data': {
                'type': 'Point',
                'coordinates': [-94, 40]
            }
        });
        map.addLayer({
            'id': 'center',
            'type': 'symbol',
            'source': 'center',
            'layout': {
                'icon-image': 'marker-15',
                'text-field': 'Center: [-94, 40]',
                'text-font': ['Open Sans Semibold', 'Arial Unicode MS Bold'],
                'text-offset': [0, 0.6],
                'text-anchor': 'top'
            }
        });

        var animateButton = document.getElementById('animateButton');
        animateButton.addEventListener('click', function() {
            var easingInput = document.getElementById('easing');
            var easingFn =
                easingFunctions[
                    easingInput.options[easingInput.selectedIndex].value
                ];
            var duration = parseInt(durationInput.value, 10);
            var animate = animateValue.checked;
            var offsetX = parseInt(
                document.getElementById('offset-x').value,
                10
            );
            var offsetY = parseInt(
                document.getElementById('offset-y').value,
                10
            );

            var animationOptions = {
                duration: duration,
                easing: easingFn,
                offset: [offsetX, offsetY],
                animate: animate,
                essential: true // animation will happen even if user has `prefers-reduced-motion` setting on
            };

            // Create a random location to fly to by offsetting the map's
            // initial center point by up to 10 degrees.
            var center = [
                -95 + (Math.random() - 0.5) * 20,
                40 + (Math.random() - 0.5) * 20
            ];

            // merge animationOptions with other flyTo options
            animationOptions.center = center;

            map.flyTo(animationOptions);
            // update 'center' source and layer to show our new map center
            // compare this center point to where the camera ends up when an offset is applied
            map.getSource('center').setData({
                'type': 'Point',
                'coordinates': center
            });
            map.setLayoutProperty(
                'center',
                'text-field',
                'Center: [' +
                    center[0].toFixed(1) +
                    ', ' +
                    center[1].toFixed(1) +
                    ']'
            );
        });
    });
</script>
